Wireless communication systems of various kinds are known in the art. In general, wireless-based communication resources tend to be relatively scarce as compared to potential need at any given time (as used herein, “communication resources” tends generally to refer to bandwidth access and encompasses more particularly such elements as frequency bands, assigned frequencies and/or time slots, transmit power, spreading codes, and so forth). Consequently, conservation of communication resource allocation and usage tends to comprise an area of considerable interest and endeavor.
Many wireless communication systems utilize geographic re-use of one or more communication resources. For example, modern cellular telephony typically deploys, in a cellular fashion, a large plurality of base stations that transmit and receive using relatively low power. So configured, base stations (and/or their constituent sectors) that are located sufficiently distant from one another are able to use identical communication resources (such as a common transmit or receive frequency). This, in turn, greatly leverages the effective bandwidth and loading power of a given communication resource. Unfortunately, such distribution does not always yield the desired results.
Paging needs typify one such area of concern. There are various reasons and occasions that require a paging message to be transmitted to one or more mobile stations (as used herein, “paging” will be understood to comprise messages that are sent to the mobile station in order to elicit its response and hence facilitate ascertainment of its location within the system as well as messages that are sent to the mobile station in order to deliver a typically brief message, such as a Short Message Service message, a call-waiting notification, and the like). Such reasons and occasions, however, are often asynchronous and can occur when uncertainty may exist as regards a present precise location of the target mobile station within the communication system.
One suggested approach would cause the paging message to be transmitted from one base station at a time in seriatim fashion until the target mobile station has been located. While potentially conservative of communication resources, this approach can also consume a considerable amount of time. In many cases the required timeframe is incompatible with other needs and requirements that must be met.
Another suggested approach would have every base station transmit, essentially together though not necessarily synchronously, the paging message. This approach has the benefit of likely quickly locating the target mobile station, but also requires widespread use of communication resources, most of which are obviously not genuinely required. This approach, therefore, can significantly impact overall system throughput and bandwidth availability.
As a result, a more typical approach represents something of a compromise between these two extremes. The system identifies a base station that represents a target mobile station's last known geographic location. The paging message is then sourced using only that base station or by using a so-called Location Area Code (LAC) (or Codes) that includes this base station and other base stations that are reasonable to include (such as base stations that are neighbors of the last known location). When properly implemented, such an approach can serve in an effective and timely manner while also tending to facilitate conservation of a given system's communication resources.
Continued development and progress, however, has led to further system changes. As some networks have grown, they have outgrown their original allocated frequency band or bands (for example, in the United States, frequency bands for specific kinds of wireless services are allocated and permitted within specified frequency bands located around, for example, 800 MHz, 1.9 GHz, 2.1 GHz, and so forth). In order to grow, a given wireless communication system will often add, as a geographic overlay to an existing infrastructure of base stations, base stations that provide wireless services using a new, different band. As a result, a given geographic area may be covered by multiple base stations as correspond to different frequency bands.
In most cases, a given target mobile station will only be operating at any given moment within one band of a multi-band wireless communication system (even when the mobile station comprises a multi-band capable platform). This, of course, can lead to difficulty again with respect to transmitting a paging message to a give target mobile station in a manner that is both timely and conserving of system resources.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will also be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein.